The research which is to be undertaken or is in progress involves the preparation and study of transition metal complexes suitable for the following purposes: (1) determination of the effects of variation of structure and electronic properties on Cu(II)/Cu(I) redox potentials; (2) determination of rates of electron transfer between metal centers with well defined redox properties in binuclear complexes as a function of distance between these centers and other structural variables. The research on copper systems is directed toward an elucidation of factors which control redox potentials. Delineation of these factors might eventually allow an interpretation of the unusually high potentials found in copper proteins, and, therewith, provide information on the nature and geometry of binding sites in these proteins. Determination of electron transfer rates is being approached by the synthesis of covalently linked tetraaza macrocyclic ligands which has the potential of placing metal centers at systematically varied separations in binuclear complexes. Oxidation or reduction at one center only results in a formal mixed valence species and presents the opportunity for determination of electron transfer rates between the two centers by magnetic resonance methods. The most suitable systems for both investigations are at the present time Schiff base complexes containing two or more azomethine ligating sites.